One of the most rapidly growing markets for computer systems is the portable computer market. Recently, portable computers have become more powerful, while also becoming smaller and lighter. Furthermore, as a part of this changing market, the various computer components have become smaller and lighter while their ability to handle more data has increased.
Recently, devices have been designed that allow some of these various forms of computer components to be plugged into the same socket of a computer system, thereby reducing the space required within a portable computer. For example, an international standard which defines the physical and electrical interface specifications for the interchangeability of memory and input/output cards was introduced by Personal Computer Memory Card International Association (PCMCIA) jointly with the Japanese Electrical Industry Association (JEIDA) in September of 1991. In addition, a specification referred to as an Exchangeable Card Architecture (ExCA) specification, Dec. 20, 1991, has been issued by Intel Corporation of Santa Clara, Calif. The ExCA document describes specifications that manufacturers may use to provide interfaces which are ensured of allowing the memory and input/output cards for portable personal computers of different manufacturers to be interchanged.
A socket designed to these specifications allows cards, such as modem and flash memories to be attached, used, and removed interchangeability in the same socket. Computer systems typically include at least one socket recessed within the computer, such that the inserted components (e.g., modem, LAN, etc.) are protected by the body of the computer.
As devices and peripherals improve and advance, users often wish to upgrade their computer systems. In the prior art, to change components in a computer, the computer system had to be opened. Opening the computer system and exchanging the components is not an irregular occurrence with a personal computer. Specifically, designed circuit boards and cards are often inserted into personal computers. However, notebook or laptop computers are not regularly opened to upgrade or change the components inside. This is due to the components being designed specifically for the small dimensions of the computer casing. Anytime a computer system is opened, damage to electronic components and systems within the system may result, particularly in the case of notebook or lap-top type computers. It is desirable to be able to upgrade computer system components without having to open up the computer system.
One component which users often wish to upgrade is the microprocessor. Microprocessors in computer systems have undergone considerable advancement, usually to include additional features. The newer microprocessors often operate faster than their predecessors and also have more capabilities and functionality. When additional features are integrated in a microprocessor, its use must often require changes to the computer system to accommodate the new features. These changes could take the form of modifications to the circuit board, including the addition of new circuitry. Changes which require modifications to the bus architecture, including the bus width, are generally expensive. Ideally, new features and faster processing should be added without changing, for example, the mother board of a computer system. It is thus advantageous to upgrade a computer system to add a microprocessor that incorporates new features in such a way as to reduce or dispense with changes to the remainder of the computer system.
In the prior art, a computer system designed for a particular type of microprocessor could be upgraded with a different type of microprocessor using interface circuitry in the computer system. This interface circuitry is responsible for converting the signals to and from the newer microprocessor to a form that the computer system is designed to handle. This requires that the interface circuitry already exist in the computer system. One problem with such a solution is that the bus cycles used into the newer microprocessor are changed to those of the other processor, such that any benefits from using the newer bus cycles are negated. Also the interface circuitry can only handle a limited number (e.g., one) of upgraded processors. That is, the interface circuitry can only translate the signals of one particular upgraded microprocessor. Therefore, it is desirable to be able to upgrade components in a computer system without having to provide interface circuitry for upgrade components.
Another computer system upgrade that requires changes to the circuit board is a memory system upgrade. A memory system upgrade may constitute changing the memory components, such as changing to higher capacity components or adding one or more levels of additional memory. More and more computer systems have use for a second level cache memory. However, the addition of a second level cache to an existing computer system would require modifications to the computer system itself. It is advantageous to upgrade a computer system to include an additional cache memory without changing the computer system.
The present invention provides a mechanism for upgrading a computer system using a credit-card sized integrated circuit (IC) card. The IC card of the present invention may contain an upgraded version of the microprocessor in the computer system. Upon entry of the IC card into a slot in the side of the computer system, the on-board microprocessor is disabled and the microprocessor on the IC card acts as the microprocessor for the system without requiring special interface circuitry other than a pin-connector interface between the IC card and the computer system. The present invention also provides the ability to upgrade the memory structure of a computer system by adding a second level cache to a system that does not include one.